The Common Mechanisms of Autism and Post-Trauma

Autism and Post-Traumatic Stress Disorder (PTSD) are two mental health syndromes that have been studied extensively, and the vulnerability of people belonging to both these groups is widely known.  Until recently, however, the association between autism and PTSD has hardly been assessed.  Prof. Danny Horesh, whose research deals with PTSD and Prof. Ofer Golan, who studies autism, knew each other from the halls of Bar-Ilan University’s Department of Psychology, but did not engage in joint research until voices from the field brought the researchers back to the theoretical literature and inundated them with new questions.

Reports from patients at the clinic as well as from therapists working with people on the autism spectrum about social rejection and ridicule, which may sound trivial even if unpleasant, left the impression of an enduring experience and a strong emotional response, even after years. “It brought the two of us to meet,” Prof. Horesh and Prof. Golan relay. “One of the things that aroused our curiosity was that in research on trauma, there is almost no reference to populations with neurodiversity, and hardly any research about people with neurobiological or early-onset mental impairment. It is a historical, scientific and clinical injustice that no one is looking at what happens to these unique social groups. Are people with autism more vulnerable to trauma? Is PTSD different for them? Everything we discovered was an eye-opener for us.”

Initially it was necessary to characterize the potentially common mechanisms for people from both groups - PTSD and autism - and to see what roles they play. A study which began five years ago and was conducted in collaboration with doctoral student Nirit Haruvi-Lamdan, Prof. Nati Laor of the Center for the Treatment and Research of Autism, and a team of master’s students and research assistants, did, indeed find common mechanisms  for the two populations.

Before the study began, it was already known that people with autism and people with PTSD share several common characteristics: impaired social cognition, a tendency to have difficulty regulating emotions, differences in sensory sensitivity, and expressions of anger and aggression. Two other common and important characteristics are rumination and difficulty in processing autobiographical memory.  A tendency to ruminate is to sink into recurring thoughts, a kind of “mental repetition”.  Rumination may be positive, and that is defined as reflection, a constructive mental process, but in negative rumination (i.e., brooding), the person is stuck in thoughts like “Why did I do what I did?” or “I am guilty of trauma.” As to autobiographical memory, it is known that memory processing and event coding among people with autism is different, and it is also known that in both disorders, there are problems in processing memory. The mapping of common mechanisms for autism and PTSD appeared in a theoretical paper published at the beginning of Horesh and Golan’s joint research journey.

More Post Trauma among People on the Autism Spectrum

Later, in light of clinical evidence and existing knowledge, the researchers built a five-year research plan. "At first we examined the question from a continuous perspective, that is, with people from the general population with various levels of “autistic traits” and not with people with a clinical diagnosis of autism," they relate. "These are different characteristics such as difficulties in social communication, the need for permanence and adherence to routine, and difficulty coping with changes. In the general population one can see a wide distribution of these traits, from low to relatively high levels." Studies have found, for example, that there are higher levels of these traits among people studying exact sciences compared to people from the social sciences. The research team examined male and female students from several faculties and measured the level of autistic traits and the level of PTSD to see if there was a statistical relationship between them. "It was our first litmus paper. We found a strong bond," the researchers say. "The rate of people with PTSD was three times higher in people with a high level of autistic traits compared to people with a low level. This is a clear connection, and it gave us a reason to think that there is something about autistic traits that increases vulnerability to post-traumatic stress in the general population,” Horesh and Golan note.

At this stage of the study, it was also found that among people who had high autistic traits, the PTSD symptomatic profile was different. This manifested itself in a relatively high dominance of “hyper-arousal” symptoms and is expressed in a high degree of sensitivity and a state of increased alertness.  Seeking an explanation, the researchers related to the fact that one of the characteristics of autism is sensory hypersensitivity, which may make people on the spectrum more vulnerable. Following traumatic events, hyper-arousal may be a major problem, because people with autism tend to feel increased sensitivity to external stimuli anyway. Another finding, which has already emerged during the phase of research among the general population, relates to gender differences: the association between the cluster of post-traumatic hyper-arousal symptoms and autistic characteristics was stronger among women.

Women with Autism are More Vulnerable

The next phase focused on the central core of the study: observing a clinical group diagnosed on the autism spectrum and comparing it to a neuro-typical group, that is, from the general population, with neurological variability. Participants on the autism spectrum had age-appropriate cognitive and verbal abilities – once defined as “high functioning”. The findings were replicated, and even more so: the differences in PTSD rates between people on the spectrum and people who were not on the spectrum was very clear – 32% compared to 4% (respectively). “We tried to examine the triggers that caused the trauma, and, in fact, we expanded the observation beyond the classic triggers like war, terror, physical and sexual assault, to social triggers, like boycotts, ridicule, bullying and cyberbullying,” says Prof. Horesh. “We have seen that for people on the spectrum, social triggers are the ones most associated with PTSD, while for the neuro-typical group, these were the classic triggers.”

Another finding at this stage was that for women on the autism spectrum, the PTSD differences between the two groups were greater. “The increased vulnerability was among women, although autism is more common among men,” says Prof. Golan. “Our study suggests that women on the spectrum are more likely to experience social harm. They are more vulnerable to harm, and their distress may be greater, as compared to men.”

In the third phase of the research project, the researchers returned to the initial theoretical paper, in which they proposed common mechanisms for people with PTSD and people with autism – rumination, emotional regulation, anger and aggression, impaired autobiographical memory, social cognition problems, and sensory regulation. The aim was to analyze each one of the mechanisms and to examine its potential role in the post-traumatic vulnerability to people with autism.

An article recently published in the journal, Autism, introduced the mechanism of rumination. The researchers examined whether high levels of rumination explain the association between autism and PTSD. In other words: whether rumination empowers distress. Indeed, it has been found that brooding (incubation), which the research literature recognizes as a cause of depression and is more common among people with autism, explains why a person with autism is more likely to suffer from PTSD.

To date, the researchers have used a variety of validated self-report questionnaires, as well as several lab assignments to examine autobiographical memory and social cognition.  This year the research team will also begin conducting in-depth interviews with people diagnosed with both PTSD and autism, in order to understand their subjective experience of the trauma.  Given the nature of the study, it can be understood that people on the autism spectrum who participated in it have normal intellectual abilities. However at least 50% of the population of people with autism are diagnosed with intellectual disabilities and some even have minimal verbal abilities. Precisely for them, examining the issue of PTSD in follow-up studies may be particularly relevant.

Great Demand for Customized Care

The research of Prof. Golan and Prof.  Horesh and their colleagues has been going on for five years, and so far has yielded four articles, and the fifth is in the workings. A year and a half ago, they joined forces with the Association for Children at Risk in Israel, that treats populations with autism and those with PTSD separately. Now the association, which is professionally led by Prof. Nati Laor, is a partner in acquiring a better understanding of the connection between the two disorders.

“Since we started there has been a certain boom in the field in the world,” the researchers say. “There are teams in Canada, the US and Europe, that are looking at the link between autism and PTSD from all angles. What is lacking is the translation of the research into therapeutic practice, which, as usual in psychology, comes last.  It is difficult to find evidence of therapeutic efficacy in the population of people with both autism and trauma. Some 30% of the people with autism that participated in the study suffer from PTSD.  Since PTSD is a disorder that can occur in a huge variety of ways – some say several hundreds of thousands – it is important to understand the vast heterogeneity of populations suffering from trauma. Another problem is that many therapists tend to attribute PTSD symptoms to autism itself and, in fact, ignore the unique problems that confront a person with autism who has experienced trauma.  

 “Since we started publishing the articles, we have received letters from people with autism and their families, in Israel and abroad. They write, ‘Finally someone recognizes the existence of PTSD among people with autism, we don’t know how it is to be treated, recommend someone who can treat us.’  To the best of our knowledge, in the United States, there is only one center that deals with this. It seems that the subject very much concerns people on the spectrum. This gives us the strength to continue with our research in this important field.”